On my journey of learning electronics I pretty quickly got interested in circuits related to audio, synthesizer-like circuits in particular. I wish to thank Ray Wilson and his “Weird Sound Generator” for introducing me to the world of synth-DIY.
A friend of mine has a Coron DS-7 drum synthesizer. I found it to be fascinating and I wanted to make something similar.
Pouring over diy-builds in different forums and reading datasheets and looking at various schematics I started gathering some ideas.
The result is a simple linear VCO. It generates a square and triangle wave at one frequency and a ramp at double that frequency. The ramp is achieved by inverting the triangle wave and switching between them using the square wave to control a multiplexing IC. Surprisingly, it works pretty well.
The only exotic (not really) part is the MAX1044 IC I use to generate a -9 voltage to bias the op-amps. Everything else is TL084 quad op-amps, a CD4053 for signal switching and simple, passive components.
Next, to double the square and triangle frequencies to match the ramp, and shape a sine wave.